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Picture of the Day · NASA

Pathfinder on Mars
2026-07-04
On July 4th, 1997, using its own array of fireworks, a parachute, and a cocoon of airbags, the Mars Pathfinder spacecraft bounced like a giant beach ball at least 15 times before it came to rest on the surface of Mars at 10:07 AM Pacific Daylight Time. After its then novel airbag-assisted landing sequence was completed, Pathfinder transmitted this color mosaic to mission operators on Earth. In the scene from another world, the Mars Sojourner robot rover is visible in the foreground, crouched on top of the unfolded Pathfinder. About the size of a large house cat, the six-wheeled, solar-powered Sojourner became the first successful Martian rover. Surrounding Pathfinder are deflated airbags and the rock-strewn terrain of the Ares Vallis floodplain. In the distance Martian hills appear against a dusty brownish sky. The Pathfinder lander was subsequently renamed the Carl Sagan Memorial Station.
via NASA APOD
Key facts
- Discovered by
- A. Mrkos
- Discovery site
- Kleť Obs.
- Discovery date
- 19 April 1984
- Pronunciation
- / ˈ m ɛ n t ɔːr /
- Named after
- Mentor (Greek mythology)
- Alternative designations
- 1984 HA 1 · 1950 HG 1
- Minor planet category
- Jupiter trojan , Trojan · background
- Adjectives
- Mentorian
- Observation arc
- 35.19 yr (12,853 d)
- Aphelion
- 5.4935 AU
- Perihelion
- 4.7828 AU
- Semi major axis
- 5.1382 AU
- Orbital period sidereal
- 11.65 yr (4,254 d)
- Mean anomaly
- 236.39 °
- Mean motion
- 0° 5 4.56 / day
- Inclination
- 24.654°
- Longitude of ascending node
- 179.66°
- Argument of perihelion
- 131.49°
via Wikipedia infobox
Wikidata facts
- Instance of
- asteroid
- Named after
- Mentor
- Followed by
- Q239428
- Follows
- 3450 Dommanget
- Parent body
- Sun
- Minor-planet group
- asteroid belt
- Diameter
- 126.288
- Orbital period
- 4324.999880828438
- Image
- 003451-asteroid shape model (3451) Mentor.png
Show 19 more facts
- discoverer or inventor
- Antonín Mrkos
- site of astronomical discovery
- Kleť Observatory
- provisional designation
- 1984 HA1
- time of discovery or invention
- 1984-04-19
- orbital eccentricity
- 0.07457099181744761
- orbital inclination
- 24.57877355484928
- periapsis
- 4.807672664494592
- apoapsis
- 5.582476384185798
- semi-major axis of an orbit
- 5.195074524340195
- mean anomaly
- 109.1636663563591
- longitude of ascending node
- 179.479405894974
- argument of periapsis
- 134.7267255738195
- absolute magnitude
- 8.46
- Commons category
- 3451 Mentor
- albedo
- 0.044
- rotation period
- 7.702
- asteroid spectral type
- X-type asteroid
- time of periapsis
- 2459689.0198778277
- epoch
- November 21, 2025
via Wikidata · CC0
~5 min read
Encyclopedic overview
3451 Mentor is a large Jupiter trojan from the Trojan camp, approximately 120 kilometers (75 miles) in diameter. It was discovered on 19 April 1984, by Czech astronomer Antonín Mrkos at the Kleť Observatory in the Czech Republic. The uncommon Jovian X-type asteroid is one of the largest Jupiter trojans and has a rotation period of 7.7 hours. It was named after Mentor from Greek mythology. Mentor, a man who was rich in horse at Pedaeus. He was the father of the spearman Imbrius, an ally of the Trojans.
Orbit and classification
Excerpted from Wikipedia’s “3451 Mentor” article, available under the CC BY-SA 4.0 licence.